Lecture 4 - ECG introduction Flashcards
(29 cards)
__ is a record of the electrical activity of the heart with respect to time
ECG (electrocardiogram)
ECG is most commonly used clinical tool for ddx __. It can also give insight to heart orientation, chamber sizes, and disturbances in rhythm and conduction.
cardiac arrhythmias
when current flows from cells already depolarized to those still at rest, a __ is set up
electric field/dipole
the ECG records __ when more than one wavefront is occurring at a time
average wavefront
A __ is composed of a + and - electrode and multple ones are used to “see” the cardiac vector from different views
lead
__ there are no potential differences seen on the ECG
At rest/refractory periods (“flat line”) - when depolarization is complete. Only see vectors during depolarization.
repolarization is a __ charge (downward deflection seen), depolarization is a __ charge (upward deflection seen). This depends on where the positive charge is placed.
negative, positive
During Depolarization (cell surface becomes negative where inside of the cell is positive) a negative wave approaches the positive lead and an __ deflection is measured by the voltmeter.
upward
when the whole cell is depolarized the voltmeter will show __ across the electrodes and the line is __
no potential difference, flat (cell is now positive inside and negative outside)
if the leads were reversed and there was a depolarized/negative wave heading towards a negative pole then there would be a __ deflection
downward deflection
Repolarization is recorded as a __ deflection
downward (negative)
direction of ECG signal is dependent upon the position of the electrodes. A wave of depolarization towards the positive electrod gives a __ deflection
positive
The magnitude of deflection reflects how __ the electrical force is to the axis of the lead being examined
parallel (more parallel = taller deflection)
how do perpendicular forces register on ECG deflection?
do not register = flat line
main vector of depolarization during systole is detected from the __
left ventricle
to standardize ventricular depolarization with a positive deflection where should the negative electrode be placed
right forelimb
lead 2 is commonly used and is a __ lead system with electrodes located __ and __
bipolar (leads 1-3 are bipolar systems), negative electrode = Right arm, positive electrode = left leg
if using lead 1 the negative electrode goes on the __ and the positive on the __
right arm, left arm
if using lead 3 the negative electrode goes on the __ and the positive on the __
left arm, left leg
which bipolar lead system gives the most positive deflection
lead 2
p wave =
atrial depolarization (SA node not large enough to register)
QRS complex =
ventricular depolarization (usually largest amplitude)
T wave =
ventricular repolarization
flat line between P and QRS =
delay in conduction of AV node (AV node depolarization too small to register)
